Function array_map

src/backend/utils/adt/arrayfuncs.c:3209–3350

* array_map() * * Map an array through an arbitrary expression. Return a new array with * the same dimensions and each source element transformed by the given, * already-compiled expression. Each source element is placed in the * innermost_caseval/innermost_casenull fields of the ExprState. * * Parameters are: * * arrayd: Datum representing array argument. * * exprstate: ExprState repre

 * NB: caller should be running in econtext's per-tuple memory context.
 */
Datum
array_map(Datum arrayd,
		  ExprState *exprstate, ExprContext *econtext,
		  Oid retType, ArrayMapState *amstate)
{
	AnyArrayType *v = DatumGetAnyArrayP(arrayd);
	ArrayType  *result;
	Datum	   *values;
	bool	   *nulls;
	int		   *dim;
	int			ndim;
	int			nitems;
	int			i;
	int32		nbytes = 0;
	int32		dataoffset;
	bool		hasnulls;
	Oid			inpType;
	int			inp_typlen;
	bool		inp_typbyval;
	char		inp_typalign;
	int			typlen;
	bool		typbyval;
	char		typalign;
	array_iter	iter;
	ArrayMetaState *inp_extra;
	ArrayMetaState *ret_extra;
	Datum	   *transform_source = exprstate->innermost_caseval;
	bool	   *transform_source_isnull = exprstate->innermost_casenull;

	inpType = AARR_ELEMTYPE(v);
	ndim = AARR_NDIM(v);
	dim = AARR_DIMS(v);
	nitems = ArrayGetNItems(ndim, dim);

	/* Check for empty array */
	if (nitems <= 0)
	{
		/* Return empty array */
		return PointerGetDatum(construct_empty_array(retType));
	}

	/*
	 * We arrange to look up info about input and return element types only
	 * once per series of calls, assuming the element type doesn't change
	 * underneath us.
	 */
	inp_extra = &amstate->inp_extra;
	ret_extra = &amstate->ret_extra;

	if (inp_extra->element_type != inpType)
	{
		get_typlenbyvalalign(inpType,
							 &inp_extra->typlen,
							 &inp_extra->typbyval,
							 &inp_extra->typalign);
		inp_extra->element_type = inpType;
	}
	inp_typlen = inp_extra->typlen;